Conventionally, various target object detection devices for transmitting radio waves to detect a target object based on the echo signals of the transmitted radio waves have devised. In such target object detection devices, for example a target object detection device equipped in a ship, there may be a case necessary to discriminate unused components such as clutters, for example a sea clutter and a rain clutter, and a noise, from a target object such as another ship and a land.
For example, JP2003-172777A discloses a target detection system in which a clutter factor is detected from observational data stored in a radar map memory so as to determine a clutter level. Further, information on reliability of the observational data is provided to a user of the system according to the determined clutter level.
As a method of detecting the clutter level, JP2002-243842A discloses a detection device in which a clutter level mainly including a sea clutter is detected from a reception signal caused by a transmission pulse.
However, as shown in the above conventional arts, not only the sea clutter but a rain clutter also exists as the clutter. In the arts disclosed in JP2003-172777A and JP2002-243842A, an appropriate condition is not set for each of the plurality of clutters and, therefore, an accurate threshold cannot be set for each of the clutters.